The present invention relates to a novel polyimide and polyamic acid. More particularly, the present invention relates to a novel polyimide and polyamic acid excellent in heat resistance, mechanical properties and adhesion property, and additionally, manifesting high solvent solubility and low dielectric property, or photosensitivity of high sensitivity and high resolution. These polyimide and polyamic acid are very useful for the application of a photoresist, and very useful as an insulation film, particularly an insulation film used as a surface protective film and interlayer insulation film of a highly integrated semiconductor apparatus and highly integrated multi-layer wiring substrate.
Conventionally, a polyimide obtained by reacting a tetracarboxylic dianhydride with a diamine is used in fields of electric and electronic appliances, astronautic appliances, transport machines and the like since such a polyimide has excellent dynamical force and dimension stability and has flame retardancy, electric insulation property and the like simultaneously in addition to its high heat resistance, and expected to be used widely in fields for which heat resistance is required also in the future. Further, from the standpoint of requirement for remarkable expansion of electric and electronic appliances typified by recent computers and the like, polyimides are expected as high performance materials in may fields such as a surface protective film of a highly integrated semiconductor element, a sealing material, an interlayer insulation film of multi-layer wiring, a film-form substrate of a print wiring, and a protective film of a solar battery and the like, due to excellent heat resistance, electric property, mechanical strength and the like. Particularly, in an insulation film and a protective film of solid elements in the semiconductor industry, a polyimide resin is advantageous since it has excellent heat resistance and mechanical properties, and additionally, imparts flattening ability, processability, low dielectric property or photosensitivity and can provide a pattern forming ability.
Conventional technologies corresponding to polyimides having photosensitivity in the present invention are described in Japanese Patent Nos. 2125907 and 1976781. These are negative photosensitive polyimides having a hardening mechanism by a photo-crosslinking reaction between a benzophenone structure and an alkyl group in the skeleton (hereinafter, abbreviated as the present mechanism).
These conventional technologies specifically disclose polyimides obtained by reacting various diamines such as 4,4xe2x80x2-diamino-3,3xe2x80x2,5,5xe2x80x2-tetramethyldiphenylmethane, 2,3,5,6-tetramethyl-1,4-phenylenediamine and the like with benzophenonetetracarboxylic dianhydride. These photosensitive polyimides show a tendency of increase in photosensitivity by increase in the alkyl group content in the molecule (POLYMER ENGINEERING AND SCIENCE, MID-NOVEMBER 1992, Vol. 32, No. 21, 1623 and later). This conventional technology also discloses photosensitive polyimides having high sensitivity and high alkyl group content in the molecule. However, under current conditions, when sensitivity is desired to be increased, a diamine unit having high alkyl group content has to be designed, leading inevitably to increase in production cost.
Further, claims in Japanese Patent No. 2125907 describe that a polyimide using diaminoindan as a diamine unit is included. This resembles the structure of polyimides of the present invention (polyimide using 1,1-dimethyldiaminoindans as a diamine unit). However, regarding this diaminoindan, a literature showing specifically a production method thereof is not found at all. As the production route, there is exemplified a method in which indene is first produced as a raw material, this is nitrated and reduced to introduce an amino group, or an aromatic ring is reduced by technologies disclosed in U.S. Pat. No. 3,875,228 and the like, and further, protection of an amino group, nitration, de-protection and reduction are effected to introducing a second amino group as disclosed in a production method of JP-A No. 9-504794. Thus, production of diaminoindan is supposed to be difficult since a lot of processes have to be conducted by combining various technologies.
Yamashita et al. have suggested a possibility of increase in photosensitivity of the resulted polyimide, by controlling steric conformation in the molecule in a photo-crosslinking reaction according to the above-mentioned mechanism (Shun Yamashita, xe2x80x9cRecent Progress of Polyimidexe2x80x9d, 1992, 29 and later, 1993). This shows a possibility of increase in sensitivity by other method than the method of increasing a methyl group content in the molecule, namely, a possibility of producing a photosensitive polyimide having high sensitivity while suppressing cost for introduction of an alkyl group. However, regarding the photosensitive polyimide according to this mechanism disclosed in the above-mentioned conventional technology, it has been impossible to realize production at low cost by increasing photosensitivity conformationally to the maximum level.
On the whole, a photosensitive polyimide having high sensitivity and high resolution according to the present mechanism cannot be satisfactorily produced at low cost, and this cheap negative photosensitive polyimide having high sensitivity and high resolution has been desired to be developed.
On the other hand, JP-B No. 7-116112 reports a diaminoindan derivative together with its production method. This diaminoindan derivative is reported to be used as a raw material of isocyanates, epoxy resins, bismaleimides and the like or as a hardening agent for isocyanates or a modifier for various resins and rubbers. However, it has not been known heretofore at all that this diaminoindan derivative is useful as a monomer for polyimides and the resultant various polyimides have excellent photosensitivity and show remarkably high solvent solubility.
An object of the present invention is to provide a novel polyimide and polyamic acid excellent in heat resistance, mechanical properties and adhesion property, and additionally, manifesting high solvent solubility and low dielectric property, or photosensitivity of high sensitivity and high resolution, wherein the polyimide and polyamic acid being useful in uses such as a photoresist, an insulation film and the like, for example.
The present inventors have intensively studied and resultantly, synthesized a novel polyimide and a novel polyamic acid having a 1,1-dimethylindan skeleton in a repeating structure and found that this polyimide or polyamic acid has excellent photosensitivity and shows dielectric property and remarkably high solvent solubility, leading to completion of the present invention.
Namely, the present invention provides a polyimide having a repeating unit of the following general formula (I): 
(wherein, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and Z represents a condensed polycyclic aromatic group or at least one group selected from the group consisting of the following formulae: 
Herein, X represents xe2x80x94COxe2x80x94 or xe2x80x94C(xe2x95x90N2)xe2x80x94, Y represents a direct bond, xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94 or xe2x80x94C(xe2x95x90N2)xe2x80x94, and W represents a direct bond, xe2x80x94CH2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94Oxe2x80x94. b represents an integer of 0 or 1, m and n each independently represent an integer of 0 or 1, r each independently represents an alkyl group having 1 to 4 carbon atoms or a halogen or a phenyl group, and a represents an integer of 0 or 1 to 3.).
Further, the present invention provides a method of producing a polyimide having a repeating unit of the above-mentioned general formula (I) wherein the method uses a diaminoindan derivative of the following general formula (II) and an aromatic tetracarboxylic dianhydride of the following general formula (III) as monomers. 
Further, the present invention provides a polyamic acid having a repeating unit of the following general formula (IV): 
(wherein, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and Z represents a condensed polycyclic aromatic group or at least one group selected from the group consisting of the following formulae: 
Herein, X represents xe2x80x94COxe2x80x94 or xe2x80x94C(xe2x95x90N2)xe2x80x94, Y represents a direct bond, xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94 or xe2x80x94C(xe2x95x90N2)xe2x80x94, and W represents a direct bond, xe2x80x94CH2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94Oxe2x80x94. b represents an integer of 0 or 1, m and n each independently represent an integer of 0 or 1, r each independently represents an alkyl group having 1 to 4 carbon atoms or a halogen or a phenyl group, and a represents an integer of 0 or 1 to 3.).
Further, the present invention provides a method of producing a polyamic acid having a repeating unit of the above-mentioned general formula (IV) wherein the method uses a diaminoindan derivative of the above-mentioned general formula (II) and an aromatic tetracarboxylic dianhydride of the above-mentioned general formula (III) as monomers.
Further, the present invention provides a polyimide wherein when the optimum stabilized structure is calculated based on theoretical calculation, the absolute value |xcex1| of the dihedral angle xcex1 is in the range from 82xc2x0 to 98xc2x0 in a repeating unit structure contained in the molecule (herein, xcex1 is a dihedral angle formed by four adjacent atoms, C(carbonyl carbon of imide)-N(nitrogen of imide)-Cxe2x80x94C, and defined in the range from xe2x88x92180xc2x0 to 180xc2x0.).